β‐Cyclodextrin inclusion enhances the pro‐resolving effects of the annexin A1 mimetic Ac2–26 in a mouse model of antigen‐induced arthritis

BACKGROUND AND PURPOSE: Rheumatoid arthritis is an inflammatory disease characterized by joint inflammation and pain. Therapeutic strategies that stimulate the resolution phase of inflammation have gained attention. Ac2-26, a mimetic peptide derived from annexin A1 (a pro-resolving mediator), exhibits pro-resolving and anti-inflammatory properties, but its therapeutic potential is limited by poor aqueous solubility and rapid clearance. Here, we investigated whether Ac2-26 included in hydroxypropyl-β-cyclodextrin (CDX-Ac2-26) enhances its pro-resolving efficacy in an antigen-induced arthritis model. EXPERIMENTAL APPROACH: Arthritic BALB/c mice were treated with either free Ac2-26 or CDX-Ac2-26 at doses 150, 50 and 15 μg per mouse (i.p.) at the peak of inflammation. Leukocyte recruitment, neutrophil apoptosis and efferocytosis were determined by cell morphology and flow cytometry. Cytokine levels were quantified by ELISA, mechanical hypernociception by electronic von Frey testing, and MerTK and CD47 expression were determined by flow cytometry. KEY RESULTS: CDX-Ac2-26 at a dose of 50 μg per mouse was sufficient to resolve inflammation, whereas free peptide required the highest dose to achieve similar effects. CDX-Ac2-26 increased the expression of full-length AnxA1, reduced accumulated neutrophils within the knee joint, decreased levels of CXCL1 and IL-1β in periarticular tissues, improved histological outcomes, and alleviated pain. These effects were associated with enhanced apoptosis and MerTK-mediated efferocytosis, along with decreased expression of CD47, a 'don't-eat-me' signal. CONCLUSIONS AND IMPLICATIONS: Inclusion of Ac2-26 in cyclodextrin enhances its biological effects at lower doses and may represent a promising therapeutic strategy to promote inflammation resolution.